Current pavement marking color specifications are given in terms of a single color with no indication of acceptable tolerances. Recently proposed standards include tolerances, but proposed tolerances are not based on psychophysical data. Although there is a substantial body of research regarding visibility of pavement markings (which is primarily related to reflectivity) very little has been done to test their discriminability (which relates to color). This research compared data obtained with a color scaling procedure, measures of existing markings, and proposed standards. Fifteen older and fifteen younger normal subjects and four color-deficient subjects participated in the color scaling study. Pavement and marking colors were simulated in the laboratory on a color monitor. Older and younger subjects judged colors similarly, but there were notable differences between the color judgments of normal and color-deficient subjects, especially under nighttime viewing conditions. The findings from this study indicate that it is reasonable to specify a range of chromaticities acceptable for pavement marking colors that will be useful during both daytime and nighttime viewing and on a variety of pavement types. Modifications to the current proposed tolerances are suggested in light of the color scaling data.